Logos and various designs have been applied to the front panel of caps for many years. The original way of applying these logos or designs was by making a patch and then sewing the patch to the front of the cap. This process, however, proved to be quite time consuming and expensive and has been substantially replaced by two methods presently in use.
One of these methods involves a heat transfer process. With this process, the printer generally orders appliques which are manufactured with the chosen design. In a few instances, a printer may have sufficient machinery himself to produce the appliques but this is generally not the case. Once the printer receives the appliques, he heat-seals them to the front panel of the caps. Drawbacks of this process include the time and cost required to have the appliques produced, usually by another company, and the fact that after a certain period of time, the appliques crack and peel. In addition, when smaller follow-up orders are received by the printer, it is generally not worth the cost of re-ordering extra appliques to fill these orders. For these reasons, a number of printers have begun using the process commonly known as silk-screen printing.
With silk-screen printing the printer first stretches the silk-screen or man-made mono-filament over a frame. To assure that there is no distortion when printing, the tension must be the same on all parts of the screen. A photograph is then taken of the chosen design and the image from the photograph is transferred onto the silk screen by a process well known in the art. After the image has been transferred onto the screen, an ink is spread over the entire screen. When the ink dries, it seals the silk screen except in those areas now containing the image. In order to print the design, one simply applies the screen to the material being printed on and with a squeegee runs some ink over the back of the screen. The ink travels through those portions of the screen which have not been sealed thereby transferring the design to the material. When the printing is completed, the frame is removed and stored in case of future orders. Thus, most printers have a large inventory of mounted silk screens which can be reused for filling follow-up orders.
Several of the advantages of silk screen printing include the speed with which a silk screen can be prepared generally by the printer himself, and the fact that the screen is always available for follow-up orders. Also, by using silk screens, printers have successfully avoided the difficulties of having the design crack or peel. For these reasons, the use of silk screen printing has been widely accepted. However, when applied to the printing of caps, a number of difficulties have been encountered which have prevented cap printers from taking full advantage of the silk screen process. Some of the difficulties unique to cap printing include trying to print onto a normally rounded surface and mounting all the caps in the same position so that the caps and the silk screen are properly aligned thereby avoiding crooked or off-centered impressions. This alignment is commonly referred to as registration.
When one prints onto the rounded front panel of a cap using a flat silk screen, a distorted impression is obtained. This is due to the fact that the pressure between the screen and the material being printed upon will vary with more pressure being applied at the top of the curve of the cap. This variation causes differences in the spreading of the ink as it passes through the silk screen and thereby causes distortion of the design applied to the cap.
In an attempt to overcome this shortcoming, two approaches have been used. The first uses a curved silk screen which matches the curvature of the cap being printed upon. The second approach uses a flat platen and attempts to flatten the curved front panel of the cap. Neither of these approaches have been successfully implemented and therefore, there was still a need for an accurate and clear printing silk screen cap printer. It was in light of this situation that we first began developing our invention.
During the initial steps of development, experiments were done with curved silk screens. However, use of a curved silk screen proved to be both impractical and expensive. The first difficulty of working with a curved frame involved the stretching of the silk screen over the frame. Due to the curvature, it was more difficult to obtain an equal tension throughout the screen. A variance in this tension would lead to a distorted image when the printed ink was passed through the screen.
The curved frames were also found to be significantly more expensive than the flat ones which are used by most printers. Due to the higher cost of the curved frame, it was impractical to store the silk screens in their mounted positions and therefore the screens had to be removed from the frames. Once the screen was removed from the frame and the tension was released, the screen would return to its normal size. When the screens were reframed, it was necessary to stretch them to the same degree that they had been stretched initially. When the silk screen was not reframed with the same degree of tension, the image produced was distorted.
One other difficulty involved matching the curvature of the frame and its associated silk screen to the cap being printed upon. In those situations where the curvature of the screen did not match the curvature of the cap, distortions would occur similar to those described above when a flat screen was applied to a rounded surface. Due to the numerous difficulties in dealing with a curved silk screen, we turned our efforts to the development of a silk screen printer which utilized a flat printing surface.
In the area of silk screen printers which utilized flat platens, the prior art had been unable to sufficiently flatten the front panel of the cap and anchor the cap so that it would not move during printing. In order to flatten the normally curved front panel of the cap, a certain amount of tension needs to be applied to the cap especially across the front panel. Those inventions which failed to provide for such tension found that the cap would move when the silk screen was applied and the front panel would often wrinkle. Those devices which did apply tension to the front panel of the cap did not apply the tension evenly. This caused distortions for two reasons. First, when the cap was removed from the printer, the stretched portions would return to their normal size. Those areas which were under greater tension would contract to a greater degree thereby producing unacceptable distortions in the design. Secondly, the variation in tension often caused creases along the front panel which prevented even printing. In addition, when mounting the caps on the prior devices it could not be determined whether or not the caps were being mounted in the same position each time. Therefore, the design was not transferred onto the same portion of the front panel of each cap.
Being familiar with the shortcomings of these cap printers, there were several features which we realized would be necessary to produce a successful silk screen cap printer. First, when the cap was mounted upon the printer, the tension across the front panel would have to be fairly equal at all points. Second, the screen and the cap would have to align in the same way for each printing. Third, the normally curved surface of the cap would have to be converted to a flat surface suitable for printing. Fourth, the cap would need to be mounted onto the printer in such a way that it would not move during printing.
When developing the present invention we sought to provide a printer capable of blocking a cap during printing. For the purposes of this application, "blocking" refers to the providing of interior supports at specific areas within the cap to avoid the creasing which would interfere with the flatness of the front panel of the cap being printed upon. This blocking also serves to maintain the cap in proper alignment during printing.
Thus, it was a primary object of this invention to provide a cap printer which would maintain the front panel of the cap flat so that there would be parallel printing surfaces.
Another object of this invention was to develop a printer wherein each cap when mounted would have the same aligned relationship with the silk screen.
Another object was to provide a printer wherein any tension applied to the printing surface would be applied evenly across the entire surface.
A still further object of this invention was to develop a printer which would secure the cap and thereby avoid movement during printing.
In general, this invention was developed to provide a printer wherein the design being transferred would not be distorted and wherein the design would also be centered in the same position on each cap.
Briefly described, the present invention has a saddle upon which the cap is mounted. The saddle has a flat platen over which the front panel of the cap is placed. A registration plate is mounted in a spaced-apart perpendicular relationship to the platen so as to define a channel between them into which the sweatband of the cap can be inserted. This relationship provides for the same registration of each cap since the registration plate serves to center the cap upon the saddle thereby assuring that the design is applied to the same part of the cap each time a cap is printed. In order to prevent the cap from creasing along the front panel, and to secure the cap during printing, the saddle is designed to support various portions of the interior of the cap thereby blocking the cap. A silk screen and frame attached to the printing device moves between an advanced and a retracted position such that the advanced position puts the screen in parallel contact with the front panel of the cap and the retracted position provides sufficient room for the cap to be removed from the saddle.
Also briefly described, the present invention includes a method for silk screen printing which involves mounting the cap on the saddle so that the cap is blocked. The cap is positioned so that the bill presses against the registration plate which is positioned in a spaced-apart perpendicular relationship to the flat platen. When the cap is pulled from the rear, the front panel is stretched across the platen thereby flattening it during the application of the silk screen. When applying this process, the sweatband of the cap resides in the space between the platen and the registration platen.